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Патент USA US2398001

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Putented Apr. 9, 1946
2,398,001
UNITED STATES PATENT oer-‘Ice
2,398,001
INSULATING MATERIAL
Cli?ord 1. Barley and Mervin E. Martin, Cumber
land, Md., assignors to Celanese Corporation of
America, a corporation of Delaware
No Drawing. Application June 1-1, 1942,
Serial No. 446,614
(Cl. 106-122)
from the body of the shaped cellulose ester leav
This invention relates to insulating material,
' 6 Claims.
and relates more particularly to insulating ma
terials having a basis of regenerated cellulose.
.The present application is a continuation in
part of our copending application S. No. 398,547,
ing behind a cellular mass or structure.
By yet another method, a product having pores
of substantially uniform size may be obtained
without the necessity of incorporating inorganic
matter therein. In accordance with the latter
?led on June 18, 1941.
process. there is added to the cellulose ester in
An object of our invention is the production of
?nely divided form, a volatile liquid or mixture of
heat insulation materials from materials having
liquids having, in the vapor state, at least a sol
a basis of regenerated cellulose of a cellular
structure.
10 vent, swelling or softening action thereon, and
the mixture is subjected to the action of elevated
Another object of our invention is the produc
temperature and pressure in a closed chamber.
tion of heat insulation material of low density
Examples of the liquids or liquid mixtures which
which may be easily fabricated in any desired
shape.
‘
Still another object of our invention is the pro
duction of heat insulation material which is rela
may be employed are acetone, ethyl alcohol, ethyl
alcohol and benzol, water, chloroform, ethylene
dichloride, acetone and ethyl or methyl alcohol,
tively inexpensive, highly'reslstant to the action
ethylene dichloride, and ethyl or methyl alcohol,
of organisms such as fungi, and which has a low
methyl chloride and ethyl or methyl alcohol, bu
speci?c thermal conductivity.
tanol, diacetone alcohol, and gasoline hydrocar
Other objects of our invention will appear from 20 bons, as well as mixtures of organic liquids with
the following detailed description.
various amounts of water. While all these liquids
Materials having a cellular structure have long
been employed for insulation purposes. The ma
are suitable, acetone, butanol, ethyl alcohol, and
is that the pore size is variable and irregular, and
there is di?iculty in ensuring that all of gas
generating solid is decomposed. In accordance
temperatures.
mixtures of these liquids with water or benzol,
are preferably employed. The conditions of ele
terial most commonly employed has been cork,
which has usually been employed in the form of 25 vated temperature and pressure are maintained
until the cellulose ester is at least partially con
boards of varying thicknesses. The cork board
verted and the pressure is then suddenly released.
is prepared by compressing particles of ?nely
The sudden release of the pressure while the
divided cork, with or without some binding ma
treated material is at an elevated temperature
terial, under sufficient pressure to cause the par
ticles to adhere. In place of cork, it has been 30 allows the liquid absorbed therein to vaporize
with extreme rapidity and the cellulose ester is
proposed to prepare insulating materials from
expanded to a strong, ?lm, cellular material of
other materials having a cellular structure, such
low density and even texture suitable for many
as, for example, those prepared from thermoplas
purposes. Among the uses of the product of this
tic materials having a basis of a cellulose ester.
Such cellular materials have been prepared 35 process is the employment of the expanded ma
, terial for thermal insulating processes. When
in several ways. According to one method the cel
forming a board from the comminuted material
lulose ester is dissolved in a solvent to produce a
made in accordance with this prior process by
viscous solution and there is incorporated therein
subjecting the latter to pressure in the presence
a solid which is capable of being decomposed by
heat or chemical treatment to yield a gas. After 40 of a binding agent, the necessary pressure often
destroys the cellular character of the material.
the solution has been set, or substantially set, the
Such change substantially reduces the thermal
mass is then treated so as to decompose the gas
e?iciency of the material. Also due to the ther
generating solid and the generation of the gas
moplastic nature of the material its scope of
therefrom causes the formation of hollow spaces
throughout the mass, resulting in a porous or cel 45 usefulness is circumscribed because of the fact
that it is subject to some deformation at elevated
lular structure. The disadvantage of this process
We have now discovered that insulating mate
rial of high thermal efficiency having certain ad
with another method, a solution of a cellulose 50 vantages over the insulating material of the prior
processes may be prepared by uniting commi
ester in a volatile solvent is prepared and soluble
nuted, regenerated cellulose materials prepared
inorganic salts of appreciable particle size are
by the saponificiation in whole or in part of dis
mixed therewith. After the solution has been
crete particles of expanded cellulose ester mate
suitably shaped and then set by removal of the
solvent, the soluble salts are extracted with water 55 rials. In accordance with our invention, expand
2
2,398,001
ed cellular material havinga basis of a cellulose
ester obtained for example, by any of the proc
esses outlined above, is reduced to a comminuted
form and the resulting cellular material of small
particle size is subjected toythe action of a suit
The saponi?cation and washing may comprise
.a batch process or it may comprise a continuous
process, the discrete cellular particles of the cel
lulose ester being carried through the saponify
ing bath at any desired speed as by a screw con
able saponifying bath. ,The regenerated cellu
veyor or the equivalent, followed by washing in
lose particles obtained in this manner retain the
a similar manner.
After washing, the regener
ated cellulose particles may be dried.
cellular structure originally present. When such
The size of the discrete particles employed in
particles are set in the desired form by means of
a suitable binding agent, the resulting product 10 the production of insulating material in accord
is a material of low density possessing a hi h
ance with our invention has a de?nite bearing
thermal insulating efficiency, as indicated by its
on the properties of the ?nal product. If the par
ticle size too closely approaches the size of the
low heat transfer coefficient. Not only may the
cellular, regenerated cellulose particles be set in
individual cells present in the structure, the cel
any desired shape, in accordance with our novel 15 lular character will largely be destroyed and the
effect of temperature and pressure will cause the '
process, but/the product thus obtained may be
product to be substantially solid in character
cut, sawed, “nailed, etc. and may be employed
rather than cellular, since the material being
wherever insulation material is necessary or de
subjected to treatment will be more in the na
sirable. In lieu of binding the particles with a
suitable binding agent, the cellular particles may 20 ture of a powder substantially devoid of cells.
For this reason the average particle size should
also be employed for insulating purposes .in a
be at least larger than the average size of the
loose form. When employed in this manner, the
cells so that the cellular nature of the material
cellular particles may be placed in air spaces sur
may be retained. The size of the particles may,
rounding the chamber to be insulated and in this
way an improved insulating effect may be ob
tained.
25 of course, be considerably larger than this.
To enable the regenerated cellulose particles
Conveniently, the saponi?cation of the cellular
materials may be carried out by treatment with
organic saponifying agents such as for example,
to be formed'into a ?rm mass, the particles are
or other organic base, or it may be carried out
with inorganic agents, such as for example, so-v
a derivative of cellulose, such as cellulose acetate,
dium hydroxide, potassium hydroxide, sodium
silicate, ammonium hydroxide, sodium carbonate
in the form of a solution, or applied as a powder
an aqueous or an alcoholic solution of the sa
ticles of regenerated cellulose, the binding agent
held together by a suitable binding agent. Thev
binding agent may be a glue, such as casein glue,
methyl amine, ethylene diamine, triethanolamine 30 animal glue or vegetable glue. It may also be
or a resin or gum, applied with a volatile solvent
mixed with the regenerated cellulose and then
or other inorganic basic agent. The saponifying 35 treated with a solvent to effect a binding of the
particles. It may, however, be an inorganic bind- agents may be employed either in aqueous or in
ing agent such as, for example, sodium silicate.
alcoholic solutions. Preferably, we employ aque
In some cases it is desirable to employ a binding
, ous solutions of sodium hydroxide.
agent such as a natural or synthetic thermoplas
The sapom'fying solutions employed may be
of a concentration of from 1 to 8% by weight de 40 tic or thermosetting resin in gum or powder form,
and, after mixing the binding agent with the re
pending upon the particular agent employed.
generated cellulose, subjecting the mixture to a
In the case of sodium hydroxide, we preferably
shaping operation under the action of heat and
employ aqueous solutions of a concentration of '
from 2 to 5% by weight. While the entire sa 45 pressure. A partially polymerized binding agent
may also be employed, and after shaping the par
poni?cation may be carried out employing either
ponifying agent, the saponi?cation process may
also be effected by the use of both an aqueous and
an alcoholic solution of the vsaponifying agent.
Thus, the saponi?cation may be initiated by em
ploying an alcoholic solution of a saponifying
agent and may be completed with an aqueous so- _
lution of the same or a different saponifying
may be further polymerized in situ to form a
‘ shaped insulating material.
Examples of suit
able synthetic resins are phenol-formaldehyde
products, cumaron resins, glyptal resins, poly
merization products of vinyl compounds, and
the like, while suitable natural resins are ob
lophony, balsam, copaiba, dammar, elemi and
mastic. The binding agent may be employed in
agent. The ‘complete saponi?cation of the cel
lulose ester material may also be carried out by 55 an amount ranging from 1 to 5% on the weight
of the regenerated cellulose particles. The vola
reversing these steps, i.v e. by ?rst employing an
tile solvent employed may be acetone, diethyl
aqueous solution of the saponifying agent and
ether ethyl acetate, carbon tetrachloride, ethyl
then completing the saponi?cation with an al
alcoh\ 1, methyl alcohol, or the like.
coholic solution of the same or a different agent.
Between each saponi?cation step, the material 60 _ The cellular product of this invention may be
may be washed with water if desired.
The saponi?cation may be continued until the
used as insulating material in any convenient
manner. For insulating material in the form of
board, a thin layer of the mix may be shaped
cellulose ester comprising the cellular material
is completely saponi?ed or it may be interrupted 65 between broad, ?at molding surfaces, while for
insulating material of other shapes, suitably
before complete saponi?cation has been effected,
shaped
molds may be employed. The mix may
e. g. when the cellular material has .been saponi
also be extruded in the desired shape through
?ed so that it loses about 25% of its weight.
suitably shaped ori?ces by means of a screw
Thus, the saponi?cation may be carried out for
stuffer, or the like. After being suitably shaped
from 1/,» to 5 hours and at a temperature of» from 70 the insulation material may be treated or coated
20 to 100° C. depending upon the concentration
in any manner to render it water-proof or water
of the saponifying agent, and the speed and de
resistant. Such treatment may comprise sealing
gree of saponi?cation desired. When saponi?ca
the surface with a water-proo?ng material such
tion has proceeded to the desired extent, it may
as pitch or other water-insoluble or water-re
be halted by washing the particles with water.
sistant coating, or treating the formed insulat
3
2,898,001
ing material with formaldehyde or the like to
render the regenerated cellulose water-resistant.
when the boiling point is reached, the heat source _
is removed and the reaction mixture continues to
boil due to the exothermic nature of the reaction.
After about 3 to 4 minutes, the polymer which
forms becomes insoluble in the solution and sep
When used in a loose form the cellular particles
may be blown into the air spaces or placed there
in in any other convenient manner.
In order further to illustrate our invention but
without being limited thereto, the following ex
amples are given.
-
Example I
200 parts by weight of cellulose acetate having
arates. Polymerization ceases. The resin is
washed with water, an excess of sodium carbon
ate added, and the resin stirred to permit com
plete neutralization of the sulfuric acid in the
10 resin. The resin is then washed several times
with water with agitation, the water decanted or
an acetyl value of 54.5% (calculated as acetic
acid) is ground until it is of 20-30 mesh ?neness
otherwise removed, and the resin dissolved in
acetone, three parts acetone by weight to one
and mixed thoroughly with 20 parts by weight of
part resin by weight.
'
butanol. The mixture is heated at 200° C. for 1 15' The mixture of resin and cellular regenerated
minute under a pressure of 3000 lbs/sq. in. gauge.
cellulose particles is heated in a mold at'l50° C.
The pressure is released suddenly and the cellu
for 30 minutes under a pressure of 2 pounds per
lose acetate allowed to expand to ‘its maximum
square inch, the elevated temperature causing the
volume. The mass is broken up into small par
acetone solvent to evaporate and the resin there
ticles of about 0.5 to 1.0 cm. square. The ex
in to polymerize further, rendering the resin in
panded cellulose acetate particles are saponi?ed
soluble in acetone and other organic solvents.
for 3 hours with 1340 parts by weight of a 5%
This polymerization cements the particles of re
solution of sodium hydroxide maintained at 50° C.
generated cellulose into a firm coherent mass.
The regenerated cellulose particles are washed
The density of this material is 0.16 and it has a
free of alkali and dried at 100° C. for 2 hours.
heat transfer coe?lclent of 0.2 cal./hour/cm.=/
75 parts by weight of the dried, regenerated
°C./cm.
cellulose particles are mixed with 75 parts by
weight of a 15% solution of cellulose acetate hav
ing an acetyl value of 40%v in a 85/15 acetone/wa
ter solvent.
While our invention has been more particular
ly described in connection with the use of cel
lulose acetate in the preparation of our novel in
The mixture is placed in a square 30 sulating material, other cellulose esters may also
mold and maintained at 120° C. for 1/g hour.
The ?rm cake obtained in this manner is main
be employed. Examples of other cellulose esters
are cellulose propionate and cellulose butyraig,
tained at 100° C. to remove all of the residual
mixed esters such as cellulose acetate-propionate
and cellulose acetate-butyrate, and inorganic
esters, such as cellulose nitrate, preferably of low
nitrogen content. Where cellulose acetate is em
ployed it may have an acetyl value of 40% to
acetone. The product has a density of 0.16 and
a heat transfer coe?lcient of 0.201 cal./hour/
cm."/°C./cm. A cork board of similar dimensions
has a heat transfer coe?icient of 0.335, employ
ing the same units.
Example II
Regenerated cellulose insulating material inv
cake form is prepared in accordance with Exam
ple I. 10 parts by weight of the material is
treated at 150° C. for 45 minutes with 100 parts
by weight of 40% commercial formaldehyde at
a pressure of 50 lbs./sq. in. The material is dried
at 100° C. for 12 hours to remove the remaining
formaldehyde. The resulting product is mois
62.5% , determined 'as acetic acid.
In order to increase the strength or to modify
40
the appearance or properties of the objects being
molded or extruded, ?brous or other ?llers'may
be incorporated therein. Examples of such ?
brous ?llers are ?bers of cotton, ?ax, hemp, ramie,
jute and natural silk, while examples of other
?lling materials are cork, sawdust, wood shav
ings, clay, asbestos, etc., or mixtures of these.
In addition, pigmentsmay be incorporated in the
material or the material may be dyed to obtain
color effects. Suitable ?re-retardants such as,
ture-proofed. It has a density of 0.166 and a
heat transfer coemcient of 0.238 cal./hour/ 50 for example, NaI-ICOa, NaaP04, SnCl: and MgSiOa
may also be incorporated in the insulation ma
cm.=/°C./cm.
Example III
terials to reduce any ?re hazard.
It is to be understood'that the foregoing de
200 parts by weight of cellulose acetate having
tailed description is merely given by way of illus
an acetyl value of 54.5 (calculated as acetic acid) 55 tration and that many variations may be made
is ground until it is of 20-30 mesh ?neness and
therein without departing from the. spirit of our
mixed thoroughly with 20 parts by weight of a
invention.
- 50%-50% mixture by volume of ethyl alcohol and
Having described our invention, what we desire
benzoi. The mix is treated as inExample I for ex
to secure by Letters Patent is:
pansion. The disintegrated pieces are saponi?ed 60
1. Process for the production of heat-insula
in 2,000 parts by weight of 5% alcoholic potas
tion material from a cellulose ester of cellular
sium hydroxide solution at 76° C. for 1 hour. The - structure, which comprises saponifying discrete
particles of regenerated cellulose are then
particles of a cellulose ester of a cellular struc- "
washed several times with water, given a soak
ture to obtain a regenerated cellulose of cellular
ing for 1 hour in 1 liter of 1% aqueous acetic 65 structure, mixing said regenerated cellulose with
acid, washed acid free, and dried at 100° C. for 2
a solution of an adhesive binder in a volatile
hours.
solvent and subjecting the resulting mixture to
75 parts by weight of this material is mixed
a shaping operation at elevated temperature.
with 10 grams of a solution of partially poly
2. Process for the production of heat-insula
merized phenol-formaldehyde resin, the resin so 70 tion material from cellulose acetate of cellular
lution being prepared as follows: 2 parts by
structure, which comprises saponifying‘ discrete
weight of 40% formalin solution containing 1% '
particles of cellulose acetate of a cellular struc
of its weight of sulfuric acid to act as a catalyst
ture to obtain a regenerated cellulose of cellular
is mixed with 1 part by weight of phenol. The
structure, mixing said regenerated cellulose with
mixture is heated to boiling under re?ux, and 75 a solution of an adhesive binder in a volatile
4
2,398,001
5. Process for the production of heat-insula
solvent and subjecting the resulting mixture to a
shaping operation at elevated temperature.
tion material from a cellulose ester of cellular
3. Process for the production of heat-insula
structure, which comprises saponitying discretel
tion material from a cellulose ester of cellular
particles of a cellulose ester of a cellular struc
structure, which comprises .saponifying discrete
ture to obtain a regenerated cellulose of cellular
particles of a cellulose ester of a cellular struc
ture to obtain a regenerated cellulose of cellular
structure, mixing said regenerated cellulose with
an adhesive binding agent comprising/a solution
structure, mixing said regenerated cellulose with
an adhesive binding agent comprising a solution
of cellulose acetate in a volatile solvent and sub-'
jecting the resulting mixture to a shaping opera
of a partially polymerized phenol-formaldehyde 10
tion at elevated temperature.
resin in a volatile solvent and subjecting the re
sulting mixture to a shaping operation at ele
vated temperature.
4. Process for the production of heat-insula
6. Process for the production of heat-insula
tion material from cellulose acetate of cellular
structure, which comprises saponifying discrete
'
particles of cellulose acetate of a cellular struc
tion material from cellulose acetate of I cellular 15 ture to obtain a regenerated cellulose of cellular
structure, which comprises saponifying discrete
structure, mixing said regenerated cellulose with
particles of cellulose acetate of a cellular struc
ture to obtain a regenerated cellulose of cellular
an adhesive binding agent comprising a solution
of cellulose acetate in a volatile solvent and sub?
structure, mixing said regenerated cellulose with
jecting the resulting mixture to a shaping opera
'
'’
an adhesive binding agent comprising a solution 20 tion at elevated temperature.
of a partially polymerized phenol-formaldehyde
resin in a volatile solvent and subjecting the re
CLIFFORD I. HANEYJ
sulting mixture to a shaping operation at elevated
MERVIN E. MARTIN.
temperature.
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